Why ant hills keep appearing in your lawn—and how to stop them

Here’s how to manage ant hills in your yard and garden.

You love working in your garden, and you keep your lawn healthy and lush by tackling weeds and grubs, mowing correctly, and watering the right way. But those annoying anthills just keep appearing.

Of course, anthills are not only unsightly, they’re a real nuisance for your family and pets if you end up disturbing a giant mound of stinging ants. “Not all ants make hills, but in the Southeast, you’re most likely dealing with red imported fire ants if you have a large mound,” says Faith Oi, PhD, entomologist and extension professor at the University of Florida. These are an invasive species that has spread across the Southeast.

If you’ve ever upset one of their nests, you know fire ants can sting multiple times, with the workers sending out pheromones, much like yellow jackets, to call others to the fight. “Most people have a localized reaction to the stings, but about 1 percent of the population has a systemic reaction that results in respiratory issues and anaphylaxis,” says Oi.

Although red imported fire ants (Solenopsis invicta) are the most problematic when it comes to anthills, other types of ants build mounds, too. “It’s useful to know what type of ant you’re dealing with so you choose the right management techniques,” says Eric Benson, PhD, professor emeritus and extension entomologist at Clemson University. “If you’re just treating your entire yard with chemicals without knowing what type you’re dealing with, you will knock back some of the ants, but now you could have replaced non-stinging ants with stinging ants.”

For example, pyramid ants (Dorymyrmex spp) also build mounds. But they don’t sting and are enemies of fire ants, happily devouring them. If you eliminate pyramid ants from your yard, now there’s a natural void in your garden that fire ants may fill, says Oi.

Your university coop extension service (find yours here) can help you with proper ID.

Understanding Ant Hills

Fire anthills, sometimes also called ant beds, start out small but eventually can reach a dimeter of 18 to 24 inches and a height of 18 inches. “Anthills tend to be flatter and not as obvious in sandy soil but will build up overnight after rain,” says David Oi, research entomologist with the US Department of Agriculture, Agricultural Research Center.  “In clay soils, they appear larger because they’re hard, red mounds that don’t crumble in the rain.”

If you’re not paying attention, you may not notice them until they’re quite sizable. These hills can damage lawn and garden equipment, and, of course, no one wants kids or pets getting tangled up in them. “The mound also is just the tip of the iceberg,” says Benson. “There’s a whole lot more underground you’re not seeing. The mounds are used as incubators for the ‘kids.’ The larvae, or immature ants, are moved up and down in the mound for optimal growth as temperatures change.”

How To Prevent Anthills

You’re never going to eliminate all the ants in your yard—nor should you want to because they serve a purpose in the ecological makeup of your yard, acting as scavengers, cleaning up dead insects, and aerating the soil.

But sometimes you don’t want them—especially fire ants—where they construct their nests. They’ll build anywhere they find a good spot, from manicured golf courses to your back yard. Unfortunately,  “there’s no good way to prevent anthills,” says Faith Oi. However, there are a few ways to discourage them from building in a certain location:

•  Keep your lawn maintained. “If you’re mowing regularly, the ants don’t like it,” says Benson. “Mowing helps disrupt developing mounds.”
•  Eliminate obvious food sources. Clean up fallen fruit and vegetables in your garden, and keep trash contained, says Benson.
•  Remove water sources. Fix that dripping outdoor faucet, and don’t leave out water bowls for pets if ants are a problem in your yard. “They forage for water, too, just like they do for food,” says Benson.
• Treat sooner, rather than later. With any kind of ant, it’s better to deal with them early in the season to help keep their numbers down. It’s much harder to manage if you wait until August or September when the colony is huge, says Benson.
• Use ant baits. These work by exploiting the natural behavior of ants: They forage, then bring food back to the nest and share it with each other and the queen. Eliminating the queen (or queens) is key to taking out the nest, says Faith Oi. But ensure you choose the right type of bait, and follow label instructions. “There are hundreds of ant species, so this is another reason to identify the species because it will tell you what they like to eat,” says Benson. The label will say what species the product treats. Also, make sure to use fresh bait because it doesn’t store well.
• Be patient. Baits don’t work overnight; it can take several weeks for them to be effective. But most entomologists recommend using baits instead of broadcasting residual insecticides all over your lawn because those products also affect beneficials, says David Oi.
• Repeat treatments. As the season wears on, reapply baits. “A quarterly baiting regimen is often recommended because reinfestation can occur with 6 to 8 weeks, typically from the perimeter of your yard inwards,” says Faith Oi. In addition, if a yard near you is not managed, winged reproductives will fly off to start new colonies, and that can be in your garden.
• Hire a pro. If all of this seems like too much effort (or if you are allergic to fire ants), hire a professional pest control company to tackle the problem for you, says Benson.

How To Treat Anthills

If mounds are huge, the bait won’t control all of them, so you will need to treat the mound directly, says Benson. Many entomologists recommend the “two-step” method:

1. First, broadcast a granular bait (not a granular insecticide) over the area.
2. In 7 to 10 days, if the mound still is active, use a powder, dust or liquid insecticide directly on the mounds. Follow the label instructions.

As for all those folk remedies to kill ants such as grits, club soda, essential oils, and vinegar, you’re wasting your time because they aren’t effective. While pouring boiling water on a mound will kill a few ants, it’s not practical. You’ll need to boil several gallons (and water weighs 8 pounds per gallon, so you do the math!), then haul it outside— risking scalding yourself, says Benson. You’ll also damage turf and nearby plants. It’s far more efficient and effective to take out the queen and the workers with bait.

Read the original article on Southern Living